Computational Fluid Dynamics Modeling for Cardiovascular Disease Risk Analysis in Artery Bifurcations
Open Access DepositedCarotid artery diseases, such as atherosclerosis, are significant contributors to mortality world-wide. While it is recognized that low wall-shear-stresses trigger plaque formation, specifically in the internal carotid artery sinus, there is limited understanding of why only certain patients are predisposed to form plaques. In this dissertation we will introduce a typical ‘disease-prone’ carotid artery bifurcation geometry and show that it develops pathological wall-shear-stress metrics when compared to a ‘healthy’ anatomical geometry. This study further highlights the potential role of three-dimensional vortical structures in atherosclerotic plaque formation by identifying pathological behavior of internal vortical structures and linking it to the wall-shear-stress-distribution known to critically contribute to disease onset. Furthermore, physical driving factors that determine a pathological vortex behavior are identified. Physiological pulsatile flow computational fluid dynamics simulations were performed on a ‘healthy’ and a ‘disease-prone’ carotid artery bifurcation model, both developed based on clinical risk estimations and patient-averaged anatomical features taken from the clinical literature. Geometry and flow effects were investigated separately by simulating a third ‘hybrid’ model having a healthy geometry with imposed disease-prone flow conditions. The disease-prone geometry experiences a more equal flow split at the bifurcation and larger areas of lower time-averaged-wall-shear-stresses at the internal carotid artery sinus outer wall, where plaque formation is mostly found. A main hairpin vortical structure in the internal carotid artery sinus was observed for both geometries, which locally increased instantaneous wall shear stress. In the disease-prone geometry, this vortical structure has a significantly shorter lifespan. The main vortex’s time of formation is primarily dictated by artery geometry, whereas its lifespan is determined by the flow conditions. The flow split at the carotid artery bifurcation is a promising clinical indicator for atherosclerosis risk as it can be accessed using clinical imaging, whereas shear-stress-metrics cannot. The findings imply that a long persistence of the internal carotid artery sinus hairpin vortical structure has a physiologically beneficial role by elevating local wall-shear-stresses to healthier levels, and thus lowering risk of developing atherosclerosis. The deterioration of this beneficial vortical structure, occurring under disease-prone flow conditions, is expected to play a significant role in atherosclerotic plaque formation.
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